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90 a-e-mag.com • A&E THE GUIDE 2018
by a black area in the artwork, the emulsion
will have stayed water soluble, while all the
areas exposed to the ultraviolet light will have
hardened and be less soluble. In the washout
process, the areas under the black will wash
away, creating the image to be blasted. This is
the procedure with any of the water washout
films on the market.
Since the material is wet after the washout,
it has to be dried. You could do this by hanging
the sheet up to dry, but for production, it is
best to use a dryer, which keeps a constant
temperature and allows you to dry at least four
full sheets at a time within a predictable time
period. The sheets need to reach a drying point
where there are no more moist/milky spots in
the material. At that stage, the sheet can be
adhered to a sheet of silicon release paper for
future use. Most washout films on the market
are either purple or blue.
Should you decide on the dry-processed
film, which is the only green film on the
market, then the whole washout and drying
fall by the wayside. The exposure process
stays the same, even though it is quite a bit
longer (1 1/2 to 2 minutes, compared to
20 to 40 seconds with the water washout
material). However, there are a couple of
other noteworthy differences when com-
pared to the washout films.
First, the printed image from your com-
puter has to be a negative, meaning whatever
appears as a white area in your artwork will
expose and blast. This means, if you use both
types of film or you started with a washout
film and then decided to switch, the artwork
is not interchangeable. Second, you cannot
produce stencils ahead of your blasting time
because this material cannot be stored. The
stencils are viable within a 24-hour time
period; in other words, you need to keep these
qualities in mind before choosing your resist.
The dry-processing resist, called Rapid-
Mask, comes in two thicknesses: 2 mil and
4 mil. For regular black-and-white artwork,
A larger, flatbed
exposure unit that
uses a different
type of light source:
mercury vapor lights.
These units can
accommodate up to
four full sheets of
photoresist and have
a vacuum frame built
in. Of course, it comes
at a higher price tag
(around $3,000),
but if you do high
production, it's well
worth it.
Putting the printed artwork together with the emulsion side of the film.
Washing out an exposed photoresist film.
The dryer most commonly used to dry
washed-out film sheets.